Impact® Pro Industrial Earmuffs, Headband, 30 NRR dBAmplifies ambient sound to safe 82 dB response technology revert to passive hearing protector when noise reaches 82 dB All in one up and down, on off and volume control Non deforming outer headband withstands rough treatment in the toughest workplaces Quick Click height adjustment remains fixed during wear Sound amplification allows wearers to hear important communication alarms warning signals, co workers' voices Snap in ear cushions make replacement